Like, it's probably more noticeable that you don't have any romantic or sexual relationships than it would be if you don't have any true, close, platonic connections. Romantic and sexual relationships have things that are very obvious and for the most part, exclusive to them, such as kissing, making out, sex, etc. Platonic relationships that are true and close are not as visible, they're more feelings on the inside (not to say that there's none of those feelings involved with romantic and sexual relationships). If you look exclusively at the activities done with a platonic friendship, it's not very different from an acquaintanceship, or an activity partner.
I've met people who claim they have friends, but they're just coworkers they talk to a bit, guys they play games with, or guys they see at the sports bar a lot. Not people who actually support each other or any true connection. Now granted, there's nothing wrong with having those acquaintanceships or activity partners, and it can be argued that they're necessary for a fulfilling life, but they're not the same as a true connection or friendship. If you've never had that or hadn't had it in a while, it can be hard to tell what that feels like.
The only way to make these connections is through social skills, which a lot of people lack. They lack social skills, so they don't make connections, platonic or romantic. Since romantic and sexual connections have more exclusive activities, it's more easy to notice them than the lack of true friends. So I'm wondering if all this talk about the lack of romance and sex is really just poor social skills.
I'm over 40 and my ability to "socialize" for somebody who wasn't all that social was like night and day.
Pre "adulthood" I had small but very close group of friends in middle/elementary school and then a different close group of friends in high school when I moved.
Post "adulthood" I'm always needing to be somewhere else so can't chat or am at work in places where I'm at the beck and call of customers or bosses that it would take years of 10~30 minutes of honest to goodness talking to actually make a decent social connection with a coworker enough to even begin entertaining the idea that, "Yeah, this person could be considered a friend." But never fully developing into a full friendship as ... I'm always at work or going to work so being available to be a part of somebody else's life (handing out, lending a hand, etc) is pretty much nil.
So yeah, I think you're comment is pretty spot on.